The Global Goal of the project is to develop a rapid, accurate, and inexpensive diagnostic immuno-optical biosensor for Factor V Leiden (FVL) diagnosis. FVL is the most common hereditary blood coagulation disorder, comprising 3 - 7 percent of the general population and 20-40 percent of individuals with thrombosis. The sensor will be composed of an array of two optical fibers, with each immobilized monoclonal antibodies against normal Factor V (FVN) or FVL. After FVN/FVL in the sample reacts with the corresponding antibodies, they will be probed with a fluorophore tagged another antibody to specifically quantify the amount of these two molecules in the sample. This sensor will diagnose the FVL with high specificity (vs. clotting assays), faster (vs. DNA analysis), and less expensive, and also provide the information on the degree of thrombophilia by having the amount of both FVN and FVL. This early diagnosis method prevents patients from having traumatic thromboembolic complications, by allowing them to receive immediate treatments, when needed. The specific aims to initiate the research goal are: Aim 1. Purification of FVL from homozygous FVL patients (months 0-2 4). FVL molecules will be purified from the plasma of homozygous FVL patients. Aim 2. Identification and Production of Antibodies against FVN/FV L (months 4-12). Monoclonal antibodies against either FVN or FVL have been generated. The affinity to the native form of FVN or FVL will be identified. Hybridoma cells producing proper antibodies wiII be cultured in bioreactors and purified. Aim 3. Development of Sensors for FVN and FVL (months 7-24). Protocols developed for the Protein C biosensor will be used to detect FVN and FVL on two individual fiber optic sensors and a prototype of dual sensor will be developed.